metapixel: heap-based buffer overflow in open_gif_file (rwgif.c)

Description:
metapixel is a program for generating photomosaics.

A fuzzing on metapixel-imagesize revealed an overflow. The latest upstream release was about ten years ago, so I didn’t made any report. The bug does not resides in any shared object which aren’t provided by the package. If you have a web application which relies on the metapixel-imagesize binary, then you are affected. Since the “READ of size 1” it may don’t warrant a CVE at all, but some distros and packagers would have the bug fixed in their repository, so I’m sharing it.

The complete ASan output:

# metapixel-imagesize $FILE
==24883==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000eff9 at pc 0x00000050edcf bp 0x7ffce3891f90 sp 0x7ffce3891f88
READ of size 1 at 0x60200000eff9 thread T0
    #0 0x50edce in open_gif_file /tmp/portage/media-gfx/metapixel-1.0.2-r1/work/metapixel-1.0.2/rwimg/rwgif.c:132:60
    #1 0x50a4cd in open_image_reading /tmp/portage/media-gfx/metapixel-1.0.2-r1/work/metapixel-1.0.2/rwimg/readimage.c:88:9
    #2 0x50a18b in main /tmp/portage/media-gfx/metapixel-1.0.2-r1/work/metapixel-1.0.2/imagesize.c:37:14
    #3 0x7fcc5c3a861f in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #4 0x41a1d8 in _init (/usr/bin/metapixel-imagesize+0x41a1d8)

0x60200000eff9 is located 3 bytes to the right of 6-byte region [0x60200000eff0,0x60200000eff6)
allocated by thread T0 here:
    #0 0x4d3195 in calloc /tmp/portage/sys-devel/llvm-3.9.0-r1/work/llvm-3.9.0.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:72
    #1 0x7fcc5d267392 in GifMakeMapObject /tmp/portage/media-libs/giflib-5.1.4/work/giflib-5.1.4/lib/gifalloc.c:55

SUMMARY: AddressSanitizer: heap-buffer-overflow /tmp/portage/media-gfx/metapixel-1.0.2-r1/work/metapixel-1.0.2/rwimg/rwgif.c:132:60 in open_gif_file
Shadow bytes around the buggy address:
  0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c047fff9df0: fa fa fa fa fa fa fa fa fa fa 00 fa fa fa 06[fa]
  0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==24883==ABORTING

Affected version:
1.0.2

Fixed version:
N/A

Commit fix:
N/A

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

Reproducer:
https://github.com/asarubbo/poc/blob/master/00058-metapipxel-heapoverflow-open_gif_file

Timeline:
2016-11-22: bug discovered
2016-11-22: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:

metapixel: heap-based buffer overflow in open_gif_file (rwgif.c)

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